1. Field of the Invention
The present invention is directed toward stabilizing components for use with joints of the body. Examples of such joints include hip joints, shoulder joints, elbow joints, ankle joints, and knee joints. More specifically, aspects of the present invention are directed toward biologic and biologically reabsorbable stabilizing components to at least temporarily augment a knee prosthesis to provide a level of medial, and/or later, and/or anterior, and/or posterior, and/or subluxation stability proportional to patient recover time in response to a total knee arthroplasty procedure to bridge any deficiency in stability that is a resultant of the surgical procedure.
2. Background of the Invention
A human knee joint consists of the articulation between the femur and the tibia. The femur includes a lateral condyle and a medial condyle riding upon the lateral meniscus and the medial meniscus on the tibial plateau. An intercondylar channel is formed allowing throughput of the anterior cruciate ligament and the posterior cruciate ligament.
Total knee replacement surgery begins by making an incision exposing the knee joint. The femur is separated from the tibia and the damaged portions of the femur are removed. During this procedure various ligaments are impaired or removed, potentially decreasing the medial, lateral, anterior, posterior, and/or suxluxation stability. The removal of the damaged portions leaves the femur contoured to accept a femoral prosthetic component cemented thereto. Likewise, the tibia is manipulated to remove the damaged bone and tissue, leaving a contoured aspect to receive the tibial prosthetic component cemented thereto.
FIGS. 1-5 illustrate a prior art knee replacement prosthesis that includes a femoral component 10 (see FIG. 1) and a tibial component 12 (see FIG. 2), and the interaction therebetween (see FIGS. 3-5).
The femoral component 10, adapted to be implanted on the distal end of the patient's femur, includes a pair of convex bearing surfaces 14 that are separated by an intercondylar channel 16. Provided within the intercondylar channel 16 is a posterior cam 18 and an anterior cam 20.
The tibial component 12, adapted to be implanted on the proximal end of the patient's tibia, includes a tibial insert 24 and an upper aspect 26 exhibiting a stabilizing post 28 and a pair of concave bearing surfaces 30 that receive the convex bearing surfaces 14 of the femoral component. The tibial insert 24 also includes a distal stem portion 32 for mounting the tibial component 12 to the tibia.
As the knee flexes, the femur (see FIG. 5) rotates clockwise relative to the tibial component 12. This brings the posterior cam 18 into contact with the stabilizing spine 28. This interaction prevents anterior translation of the femur relative to the tibial component 12 as the spine 28 blocks this motion. With further flexion, the interaction of the tibial insert spine 28 with the posterior cam 18 forces posterior translation of the femoral component 10 relative to the tibia (rollback). This rollback allows for optimal knee flexion.
As the knee extends beyond neutral (see FIG. 5), the anterior femoral component cam prevents counterclockwise motion of the femoral component relative to the tibia. This interaction prevents hyperextension of the knee joint.
Stability after total knee arthroplasty is a pressing problem in primary and revision total knee arthorplasty. Ligament stability can be lost from over-release of the medial collateral ligament during balancing. The ligaments about the knee are often deficient as a result of as a result of removal or damaged caused during the total knee arthroplasty procedure itself. These deficient ligaments could be reconstructed using biologic ligaments but these would need temporary support as they become competent. While a VVC (Varus/Valgus Constrainting) total knee arthroplasty with permanent cam post mechanism could be utilized, long term this constraint could result in losing at the other interfaces.